Field of the Invention
The present invention relates generally to an underground mine roof support for supporting the roof, and, more particularly, to a yieldable mine roof support that allows ventilation air to pass through the mine roof support to increase air flow within a mine entry in which a plurality of the mine roof supports according to the present invention are installed.
Description of the Related Art
Over the past several years, Burrell Mining Products, Inc. of New Kensington, Pa. has successfully marketed and sold a mine roof support product sold under the trademark THE CAN®. THE CAN support is comprised of an elongate metal shell that is filled with aerated concrete. The use of aerated concrete in THE CAN support allows the support to yield axially and/or biaxially in a controlled manner that prevents sudden collapse or sagging of the mine roof and floor heaving. THE CAN support yields axially as the aerated concrete within the product is crushed and maintains support of a load as it yields.
A typical size of THE CAN support is approximately six feet (1.8 meters) in height and two feet (0.6 meters) in diameter. The overall height of THE CAN supports is based on the average size of the mine entry with each support being of a height that is less than an average height of the mine entry in which the supports are to be installed. In order to install each support, wood planks (or other appropriate cribbing materials such as aerated concrete blocks) are placed beneath THE CAN support to level the support and additional wood planks or other cribbing materials are placed on top of the support until the space between the support and the roof is filled. Essentially, the cribbing materials are tightly wedged between the support and the roof so as to cause each THE CAN support to bear a load of the roof upon installation.
In order to adequately support the roof of a mine entry, a number of THE CAN supports are installed using the previously described method. The supports are typically installed in rows and columns according to mine engineering specifications to provide a desired level of support within the mine entry. Because a number of the supports are installed in the entry, and the fact that the supports are often staggered or offset within the mine entry, even though ventilation air can circulate around the supports, the presence of the supports within the mine entry still impedes the flow of air through the entry. Any increase in ventilation air flow is highly desired in underground mining so that fresh, breathable air is provided to mine personnel while potentially dangerous gases are evacuated and prevented from building within the mine atmosphere.
Thus, it would be advantageous to provide a mine roof support that is capable of supporting loads comparable to THE CAN mine roof support, but that also increases the flow of ventilation air through a mine entry in which such supports are installed. This and other advantages will become apparent from a reading of the following summary of the invention and description of the illustrated embodiments in accordance with the principles of the present invention.